JSON Formatter & Validator
Format, validate, and minify JSON with syntax highlighting and error detection. Runs entirely in your browser.
JSON formatter: readable data, fewer production bugs
JSON is the lingua franca of modern APIs. Pretty-printing exposes missing commas, mismatched braces, and accidental trailing text. Minifying removes whitespace for bandwidth while keeping payloads valid for clients that reject pretty output.
When to validate here: pasting sample responses from logs, preparing fixtures for tests, or teaching newcomers how objects and arrays nest. The linter feedback is immediate and private—nothing uploads to a server in normal browser-only operation.
Privacy tip: large JSON may contain tokens or PII — scrub secrets before sharing screenshots. Pair with Base64 or URL tools when debugging encoding layers.
Edge cases: duplicate keys are technically invalid per RFC but some parsers last-wins; JSON cannot have comments unless your pipeline uses JSON5—don’t assume comments are portable.
Workflow: format → visually scan structure → minify only when sending over the wire. Keep canonical pretty copies in repos for code review readability.
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Frequently Asked Questions
What does 'format' vs 'minify' do to JSON?
Formatting (pretty-printing) adds whitespace, indentation, and line breaks to make JSON human-readable. Minifying removes all unnecessary whitespace to produce the most compact form, saving bandwidth for API responses.
Why does my JSON fail to validate?
Common JSON errors include: trailing commas after the last key/value pair (not allowed in JSON), using single quotes instead of double quotes for strings, unquoted property names, or numbers with leading zeros. This validator will highlight the error location.
What is the difference between JSON and JavaScript objects?
JSON is a data-interchange format that is a strict subset of JavaScript. Key differences: JSON property names must be double-quoted strings; JSON values cannot be undefined, functions, or symbols; JSON does not support comments.
Can JSON contain comments?
No. The JSON specification (RFC 8259) does not allow comments. If you need comments in configuration files, consider JSON5, HJSON, or YAML instead.
What is JSON Schema?
JSON Schema is a vocabulary that allows you to validate the structure and content of JSON documents. You define rules like required properties, allowed types, and value ranges. It is used for API contract validation and form input validation.